Get list of all checked nodes and its subnodes in treeview

Question

I have a treeview list check boxes and the list contains nodes, subnodes and in some cases subnode of subnode. When user check some items i want to get list of selected item

Answer 1

public void GetCheckedNodes(TreeNodeCollection nodes)
{
    foreach(System.Windows.Forms.TreeNode aNode in nodes)
    {
         //edit
         if(!aNode.Checked)
             continue;

         Console.WriteLine(aNode.Text);

         if(aNode.Nodes.Count != 0)
             GetCheckedNodes(aNode.Nodes);
    }
} 

You don't make look back into the child notes, using recursion you can do it.

You need method like this ! In your code just call once GetCheckedNodes(tvSastavnica.Nodes) and all checked nodes should be displayed !

Answer 2

my way:

void LookupChecks(TreeNodeCollection nodes, List<TreeNode> list)
{
    foreach (TreeNode node in nodes)
    {
        if (node.Checked)
            list.Add(node);

        LookupChecks(node.Nodes, list);
    }
}

useage:

var list = new List<TreeNode>();
LookupChecks(TreeView.Nodes, list);

Answer 3

If you like LINQ, you can create an extension method that traverses the whole treeview:

internal static IEnumerable<TreeNode> Descendants(this TreeNodeCollection c)
{
    foreach (var node in c.OfType<TreeNode>())
    {
        yield return node;

        foreach (var child in node.Nodes.Descendants())
        {
            yield return child;
        }
    }
}

Then you can perform every operations you want using LINQ. In your case, getting a list of selected nodes is easy:

var selectedNodes = myTreeView.Nodes.Descendants()
                    .Where(n => n.Checked)
                    .Select(n => n.Text)
                    .ToList();

An advantage of this approach is it is generic.

However, because the Descendant() method traverses the whole tree, it might be a bit less efficient than the answer given by @mybirthname because it only cares about nodes that are checked with their parents. I dont known if your use case includes this constraint.

EDIT: Now @mybirthname answer has been edited, it is doing the same. Now you have the loop and the LINQ solution, both are recursive.